Expansion chamber for liquid cooled electrical apparatus



March 22, 14966 D. E. BRzEzlNsKl EXPANSION CHAMBER FOR LIQUID COOLED ELECTRICAL APPARATUS Filed Feb. l1, 1965 .n 15 M m 3,242,250 EXPANSION CHAMBER FOR LIQUID COOLED ELECTRICAL APPARATUS v Donald E. Brzezinski, Milwaukee, Wis., assignor to Wehr Steel Company, Milwaukee, Wis., a corporation of Wisconsin v Filed Feb. 11, 1963, Ser. No. 257,427 8 Claims. (Cl. 174-12) This invention relates to electromagnetic assemblies and, more particularly, to the dissipation of yheatA generated as a result of operation of such assemblies.

Electromagnets when energized generate heat and it has been proposed to position the electromagnets in an oil filled housing so that the oil acts as a heat transfer agent to conduct heat from the core and coil assembly of the electromagnet to the housing where it can be readilydissipated to the ambient atmosphere.

This invention proposes, and has as one of its objects, the elimination of pockets of air, or other gases, within the housing and also accommodate expansion and contraction of the oil (or whatever other `suitable heat conducting and electrically insulating medium is used) during operation of the magnet Without the formation of such' pockets; and to do so while maintaining a compact structure.

A further object of this invention is' to provide an electromagnetic assembly which can be used in avariety of positions and will provide optimum heat dissipation in any selected position. Y l

Another object of this invention is to provide an electromagnetic structure having improved heat dissipating characteristics.

For the achievement of these and other objects this invention proposes to locate, within a magnet housing, expansion chamber means which willallow the housing to be completely lled with oil so that the oil is in complete engagement with the inner surfaces of the housing. The expansion chamber means is constructed and arranged to receive oil as it expands due to a temperature rise and to supply oil to the housing interior to compensate for oil contraction due to a drop in oil temperature. 1n this manner, expansion and contraction of oil is accommodated without the formation of heat insulating voids or pockets. Locating the expansion chamber within the housing mainta-ins a compact structure and provides the additional advantage of permitting the expansion -chamber l(to be so located as to enhance the convective circulation of oil in the housing and to thereby effect a corresponding increase in heat dissipation. More particularly the expansion chamber is positioned intermediate and spaced from both the housing and the magnet coil and core assembly and, so positioned, actsin the nature of a heat insulating baffle to increase the temperature differential between the warmer rising oil adjacent the coil and core assembly and the cooler returning oil on the oppos-ite side of the expansion chamber. l

Furthermore, it is also preferred to utilize a restricted opening, or openings, in the lower portion of the expansion chamber to connect the expansion chamber to the housing inter-ior for a transference of oil therebetween. The opening, or openings, are arranged so that the expansion chamber can be selectively opened to the atmosphere ambient the housing and the magnet can still be used in a tilted position without the danger of air escaping from the expansion chamber into the housing interior.

Other objects and advantages will be pointed out in, or be `apparent from, the specification and claims, as will obvious modifications of the embodiments shown in the drawings, in which:

FIG. 1 is a general schematic illustration of' a typical application of this invention;

United States Patent() Patented Mar. 22, 1966 FIG. 2 is a plan view of the electromagnetic structure partially in section;

FIG. 3 is an elevation view partially in section; and

FIG. 4 is a partial view of an alternative design for the lower wall of the expansion chamber.

A typical application of an electromagnet constructed in accordance with this invention :is illustrated in FIG. 1 wherein a conveyor 10 Iis used to transport a quantity of material (not shown) past a separator assembly 12. The separator assembly includes a stationary magnet 14 associated with a conveyor belt 16 which moves transversely of conveyor10. Magnet 14 will magnetize any magnetic particles conta-ined in the material carried on conveyor 10 and will attract particles to conveyor belt16. The attracted particles adhere to conveyor belt 16 until movement of belt 16 carries the particles out of. the field of magnet 14 whereupon the particles separate from the belt for collection in any convenient manner.

Stationary magnet 14 includes an electromagnet assembly 18 positioned within a housing 20. The electromagnet comprises a core 22 yand a coil 24 which coil is connected through suitable terminals 26 and 28 to a source of electrical energy for alternate magnetization and demagnetization of the core. Heat is generated during operation ofthe electromagnet .and housing 20 is lled with oil 30, or other like heat conducting and electrically insulating medium, to provide a heat transfer agent for conduct-ing heat from the coil 'and core assembly to housing 22'. Housing 22 dissipates this heat by radiation to the atmosphere ambient the magnet and to assist in the dissip ation of heat, side walls 32`and 34 of the housing are corrugated to maximize the available heat radiating surfaces.

When the magnet is energized the Ioil adjacent electromagnet assembly 18 lis heated and, due to normal convective action, rises. lThe hot oil engages and transfers heat to upper Wall 36 -of the housing whereupon the oil is cooled and begins to return to the lower portion of the housing. The convective circulation of oil is illustrated by the arrows in FIG. 3 and during this circulation the oil engages and transfers heat to the side and top walls of the housing as well as its end walls 38 and 40.

It has been observed that particularly desirable and efiicient dissipation of lheat can be achieved by maintaining a direct, intimate contact of the oil with the upper wall 36 of the housing. To provide and maintain this contact between the oil and the upper wall of the housing an expansion chamber 42 is located `within the housing and comprises a generally elongated hollow rectangular body 44 defining a chamber having a top portion which is closed to the inter-ior of the housing Iand is connected to the exterior of the housing through a breather pipe assembly 46.- The chamber communicates with the interior of the housing through restricted opening 48 in lower wall 50 of the expansion chamber and a length of pipe 51 registering with the opening. A threaded plug 52 cooperates with breather pipe assembly 46 .and an aperture 54 in top wall 36 of the housing to provide for selective opening and closing of the expansion chamber to the atmosphere ambient magnet.

Housing 20 is filled with oil through opening 56 and during the fill operation plug 52 is engaged in aperture 54 to close the breather pipe assembly and the expansion chamber to the ambient atmosphere. With the .expansion chamber closed oil enters the expansion chamber through pipe 51 during the fill operation but, although the housing interior is completely filled with oil, the expansion chamber is only partially filled. For example the oil in the expansion chamber rises to level 58. After the housing has been completely filled, a plug is inserted in and closes opening 56 as is illustrated in the drawings and with that plug in place plug 52 can be removedv to open the expansion chamber to the ambient atmosphere, if desired. With plug 52 removed and the plug in opening 56 the housing remains completely filled with the oil in engagement with all inner housing surfaces and, if desired, oil may be added through the breather pipe assembly to raise the level of oil within the expansion chamber. After filling through the breather pipe assembly, plug 52 may be replaced or the magnet can be operated with the expansion chamber open to the atmosphere.

Completely filling the housing with oil provides for direct engagement of oil with the inner surfaces of the heat radiating walls of the housing, particularly with the upper Wall thereof, so that upon energization of the electromagnet a virtually immediate transfer of heat to all of the heat radiating surfaces of the housingy occurs without the necessity of any delay' for expansion of oil into engagement with the housing. Therefore, transfer of heat from the electromagnet assembly begins immediately as the heat is generated and` optimum heat dissipation results. As the oil is warmed by operation ofthe electromagnet assembly it expands and thisy expansion is accommodated by the expansion chamber 44, i.e. oil is received into the chamber and oil level 58 rises.y When the core and coil assembly is` de-energized, the oil cools and contracts and the expansion chamber supplies oil tothe interior of the housing to prevent the formation of voids or pockets and to maintainy direct engagement of the oil with the heat radiatingsurfaces of the housing. The direct engagement of the oil with the heat radiating surfaces of the housing is thereby maintained and when the electromagnetic assembly is subsequently energized an immediate transfer of heat will again occur.

The lower portion of the expansion chamber 44 is preferably closed by wall 50 and is only open to the interior of th'e housing through a restricted opening in this instance through the opening registering with pipe 51, which pipe extends downwardly andv terminates in spaced relation from, but in proximity to the bottom wall of the housing. With this arrangement the magnet can be used in al tilted position without the danger'of air bubbling fromy the expansion chamber into the interior of the housing to create heat insulating pockets. This arrangement is particularly advantageous in the illustrated application of this invention as frequently it is necessary, because of space limitations, toposition separator assembly 12 at an angle to conveyor 10. As an alternative to the single opening 48 and pipe S1, a plurality l of smaller openings 53 may be formed in the lower Wall 50 of the expansion chamber (see FIG. 4). In this alternative construction, openings' 53 are located adjacent the lower, inner corner of the expansion chamber to preserve the desirable feature of eliminating the possibility of bubbling air into the housing interior when the magnet is used in a tilted position. With the restricted opening located in its lower portion, the expansion chamber can be positioned within the magnet housing and the magnet still used in a tilted position, if desired, Without the danger of air escaping into the oil filled housing.

Expansion chamber 44 is preferably supported by brackets 60 and 62 in spaced relationship from the inner walls of the housing and intermediate coil and core 18 and end wall 38. When so positioned the expansion chamber functions in the nature of a heat bafe to increase the temperature differential between the warmer rising oil adjacent the coil and core and the cooler returning oil adjacent end wall 38 and, by so doing, enhances the convective circulation of oil and heat dissipation. More particularly, while the coil 4and core is energized' the oil adjacent the assembly is warmed and, by convection, rises to engage top Wall 36 of the housing; the oil transfers heat to the wall, cools andv the major portion thereof passes downwardly between expansion chamber 44 and end wall 38, during its downward travel the oil continues to give up heat to the end wall. The oil intermediate end wall 38 and expansion chamber 44 is insulated from the warmer oil intermediate expansion chamber 44 and the coil and core and will not effect the temperature of the oil adjacent the coil and core'. Similarly, the warmer oil adjacent the coil andv core assembly will not effect the temperature of that adjacent the end wall. temperature differential is provided and a more effective convective circulation of oil results. Locating the expansion chamber within the magnet housing not only provides* a more compact structure but, also, enhances convective circulation of oil for better heat dissipation.

It is also proposed to utilize an open coil structure which is preferably provided by a single annular opening 64 extending axially of the coil 24'. The single opening ispreferred since it permits circulation of cooling oil through the` coil structure while maintaining an optimum distance between core 22 andv the meanA turn of the coil so that the cooling of the coil is accomplished without adversely effecting the magnetization of the core.

It will be understood that this invention is not limitedy to magnetic structures as used in applications such as that illustrated in FIG. 1', and although the present in vention has been illustrated and described in connection with particular embodiments thereof, it will also be apparent to those skilled in the art that various changes andv modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

What I claim is:

1. A magnetic assembly comprising, in combination, an enclosure, a coil and core assembly in said enclosure, a heat conducting and electrically insulating liquid medium completely filling. said enclosure andV directly engaging the inner surfaces of said enclosure, and chamber means positioned within'said enclosure including agenerally hollow body which includes, with respect to the liquid` level in said enclosure, an upper portion spaced from the upper inner surface of said enclosure and closed to the interior of said enclosure and a lower portion open to said enclosure interior for transferring said liquid medium between said chamber means andy said enclosure interior in response to expansion and contraction of said liquid medium during` operation of said magnetic assembly, said chamber means receiving said liquid medium from said enclosure interior uponexpansion of said liquid medium and supplying said medium to said enclosure interior to compensate for contraction of said liquid medium so that said enclosure interior remains completely filled and direct engagement of said liquid medium with said upper enclosure surface is maintained vduring operation of said magnetic assembly.

2. The magnetic assembly of claim 1 including second means connected between said enclosure and said upper chamber means portion for selectively opening and closing the interior of said chamber means to the atmosphere ambient said enclosure and third means for selectively opening and closing said enclosure interior to the atmosphere ambient said enclosure so that said liquid may be filled into both said expansion chamber and said housing interior independent of each other.

3. A magnetic assembly comprising, in combination, a housing, al coil and core assembly Within said housing, a

Vheat conducting and electrically insulating liquid completely filling said housing and directly engaging the inner surfaces thereof, means defining an expansion chamber within said housing having, with respect to the normal liquid level in said housing,a top portion closed to the interior of said housing and spaced from the upper inner surface of said housing, means for selectively connecting the interior of said expansion chamber to the atmosphere ambient said housing and means for filling the interior of Accordingly, a greater p said housing so that said housing interior can be completely filled with said liquid, and means connecting said expansion chamber with the interior of said housing for transferring said liquid therebetween in response to expansion and contraction of said liquid so that said liquid expands into said expansion chamber and said expansion chamber supplies liquid to said housing interior to compensate for contraction of said liquidand thereby maintain direct engagement of said liquid with said inner housing surfaces.

4. The combination of claim 3 including closure means extending over the lower portion of said expansion chamber and including an elongated, generally hollow member defining a restricted opening in the lower portion of said expansion chamber and extending from said restricted opening and terminating in a second opening in proximity to and spaced from the lower surface of said housing.

5. The combination of claim 3 wherein said expansion chamber is a generally rectangular enclosure and said means connecting said expansion chamber with the interior of said housing comprises a plurality of restricted openings arranged, with respect to said coil and core assembly, adjacent the lower inner corner of said rectangular enclosure.

6. A magnetic assembly comprising, in combination, a housing, a coil and core assembly within said housing, a heat conducting and electrical insulating liquid completely filling the interior of and directly engaging substantially all of the inner surfaces of said housing, an expansion chamber positioned within said housing in spaced relation from said coil and core assembly and all of the inner surfaces of said housing to define a path for convective circulation of said liquid in said housing around said expansion chamber and so that said expansion chamber does not interfere with heat transfer between said liquid and the upper inner surface of said housing, said expansion chamber having a top portion which is closed to the interior of said housing, and means connecting said expansion chamber with the interior of said housing for effecting a transference of said liquid between said expansion chamber and said housing interior in response to liquid expansion and contraction of said liquid so that said liquid expands into said expansion chamber and said expansion chamber supplies said liquid to said housing interior to compensate for contraction of said liquid and thereby maintain said direct engagement of said liquid with said inner housing surfaces.

7. Apparatus of the type described comprising, in

combination, a housing, a coil and core assembly within said housing, a heat conducting and electrically insulating liquid completely filling said housing and directly engaging the inner surfaces thereof, means defining an expansion chamber within said housing in the open area of said housing interior left by said coil and core assembly, said expansion chamber having an upper portion closed to the interior of said Ihousing and spaced from the inner upper surface of said housing, means supporting said expansion chamber in spaced relationship from the inner surfaces of said housing to define a path for convective circulation of said liquid in said housing around said expansion chamber, and means disposed below the normal liquid level in said expansion chamber and connecting said expansion chamber interior of said housing for communication therebetween and transference of said liquid between said expansion chamber and housing interior in response to expansion and contraction of said liquid so that liquid expands into said expansion chamber and said expansion chamber supplies liquid to said housing interior to compensate for contraction of liquid and thereby maintain direct engagement of said liquid with said inner housing walls.

8. The combination of claim 7 including first and second means for selectively opening the interior of said expansion chamber and said housing interior to the atmosphere ambient said housing so that said housing can be completely filled with liquid engaging substantially all of the inner surfaces thereof and said engagement of said liquid with substantially all of said inner surfaces will be maintained during operation of said apparatus.

References Cited by the Examiner UNITED STATES PATENTS 1,394,143 10/ 1921 Coolidge. 1,872,245 8/ 1932 Clark 174-12 2,416,130 2/1947 Treanor 174-12 X 2,444,351 6/ 1948 Hofberg 174-12 3,043,900 7/ 1962 Reisinger 174-12 FOREIGN PATENTS 572,878 2/ 1924 France.

655,157 l/l938 Germany.

635,541 y 4/ 1950 Great Britain.

697,012 9/ 1953 Great Britain.

JOHN F. BURNS, Primary Examiner.

JOHN P. WILDMAN, LARAMIE E. AsKrN, Examiners. 

1. A MAGNETIC ASSEMBLY COMPRISING, IN COMBINATION, AN ENCLOSURE, A COIL AND CORE ASSEMBLY IN SAID ENCLOSURE, A HEAT CONDUCTING AND ELECTRICALLY INSULATING LIQUID MEDIUM COMPLETELY FILLING SAID ENCLOSURE AND DIRECTLY ENGAGING THE INNER SURFACES OF SAID ENCLOSURE, AND CHAMBER MEANS POSITIONED WITHIN SAID ENCLOSURE INCLUDING A GENERALLY HOLLOW BODY WHICH INCLUDES, WITH RESPECT TO THE LIQUID LEVEL IN SAID ENCLOSURE, AN UPPER PORTION SPACED FROM THE UPPER INNER SURFACE OF SAID ENCLOSURE AND CLOSED TO THE INTERIOR OF SAID ENCLOSURE AND A LOWER PORTION OPEN TO SAID ENCLOSURE INTERIOR FOR TRANSFERRING SAID LIQUID MEDIUM BETWEEN SAID CHAMBER MEANS AND SAID ENCLOSURE INTERIOR IN RESPONSE TO EXPANSION AND CONTRACTION OF SAID LIQUID MEDIUM DURING OPERATION OF SAID MAGNETIC ASSEMBLY, SAID CHAMBER MEANS RECEIVING SAID LIQUID MEDIUM FROM SAID ENCLOSURE INTERIOR UPON EXPANSION OF SAID LIQUID MEDIUM AND SUPPLYING SAID MEDIUM TO SAID ENCLOSURE INTERIOR TO COMPENSATE FOR CONTRACTION OF SAID LIQUID MEDIUM SO THAT SAID ENCLOSURE INTERIOR REMAINS COMPLETELY FILLED AND DIRECT ENGAGEMENT OF SAID LIQUID MEDIUM WITH SAID UPPER ENCLOSURE SURFACE IS MAINTAINED DURING OPERATION OF SAID MAGNETIC ASSEMBLY. 